The passive optical network (PON) technology is a point-to-multipoint optical fiber access technology. As shown in FIG. 1, a PON is formed by an optical line terminal (OLT) on a station side, optical network units (ONUS) on a subscriber side, and an optical distribution network (ODN). Usually, a downlink adopts a time division multiplexing (TDM) broadcast manner, and an uplink adopts a time division multiple access (TDMA) manner. The so-called “Passive” means that the ODN does not include any active electronic device and electronic power source, and is completely formed by passive devices such as a splitter, so that the management and maintenance cost is rather low.
In an optical fiber system, usually, an optical power is adopted to indicate an intensity of an optical signal, and a unit thereof is milliwalt (mw). Meanwhile, in the optical communication, the optical signals have a small power, so that the optical power is usually indicated by dBm, in which 1 mw=0 dBm. A device for measuring an optical power is connected to a system under measurement, and is configured to amplify, sample, and perform an analogue to digital conversion on a signal to be measured. The device for measuring the optical power usually only acquires an average value of a series of data, that is, the device measures an average optical power.
A measurement result of the average optical power is an average value of intensities of optical signals corresponding to “0” signals and “1” signals within a period of time. In a PON system, the ONUs can only send uplink data in time slots allocated by the OLT in a TDMA manner, that is, send the data in a burst mode, so that the distribution of 0 and 1 in the data sent by each ONU is continuously varied each time, and thus the measured average burst transmitting optical power and/or average burst received optical power are continuously changed. Meanwhile, when the intensity of the optical signal passing through a certain segment of the optical fiber is measured, the bending or aging situation of the optical fiber in the ODN may also result in the change of the measurement result. Thus, when the measurement result is changed, it cannot determine whether the change is caused by a change of the distribution of signals under measurement or caused by the bending or aging situation of the optical fiber in the ODN, that is to say, the bending or aging problem of the optical fiber in the ODN cannot be identified through the measured optical power.